Condenser comprising a delivery tube and method for operating a condenser

ABSTRACT

A liquefier with a cylindrical delivery tube comprises a rotatable spiral disposed in the delivery tube, wherein water intakes are disposed on the delivery tube. A centrifugal pump is preferably disposed downstream of the delivery tube, said centrifugal pump delivering the liquefied medium onward.

The invention relates to a liquefier with a delivery tube, which comprises an inlet and outlet and in which a thick-stock conveyor is disposed.

Such delivery tubes are used to deliver liquid and pasty media, such as for example pulp from a pulper. A generic pulper is described in EP-A-1 584 743.

During the delivery of pulp, it may happen that the delivery causes particularly high energy expenditure, because the consistency of the delivered medium produces a high resistance to the delivery. The only way to react to this is with more powerful motors, a variation of the thick-stock conveyor, such as for example in the spiral shape or the helix shape, or a change in the delivered medium.

The problem underlying the invention is to deliver the material to be delivered over fairly long distances with minimal energy expenditure.

For this purpose, a generic liquefier is presented, which is characterised in that a centrifugal pump is disposed at the outlet of the delivery tube.

A centrifugal pump with a radial or tangential outlet for the delivered medium is particularly well suited as the pump. The effect of such a pump is that a medium liquefied in the cylindrical delivery tube is then delivered in a pumpable state via a pump into a pipe, through which the medium is delivered onward as result of the pump power.

The centrifugal pump can be used as a homogenising, i.e. de-agglomerating, pump or as a mixing pump. Such open pumps not only have the property of also being capable of processing inhomogeneous materials containing large pieces. They also break up fairly large wooden parts, which can then easily be separated in a cyclone. It is advantageous if the centrifugal pump is operated at such a high speed that it develops a sufficiently high striking force in order to break up wooden parts with a length of more than 5 cm.

Although the water supply increases the delivered volume, it is proposed that a main liquid intake is disposed at the outlet of the preferably cylindrical delivery tube and before the centrifugal pump.

The main liquid intake can have a directional component in the direction of the axis of the delivery tube. The effect of this is that the supplied liquid accelerates the material in the delivery tube in the axial direction of the delivery tube.

Cumulatively or alternatively, the main liquid intake can have a directional component in the direction of a circumferential line of the delivery tube. For this purpose, the intake can be flange-mounted tangentially. The delivered medium thus acquires a swirling motion, which is particularly advantageous if the medium is delivered onward with a centrifugal pump.

A funnel, which narrows the delivery cross-section, can be disposed at the outlet of the delivery tube. This funnel leads to a resistance, but also to an increase in the delivery rate of the liquefied medium and facilitates the introduction into a downstream conveyor. At least one liquid intake is disposed in the region of the funnel. The liquefaction can thus take place in the region of the funnel and the metering of liquefaction water in the cone ensures that a high stock density can be maintained in the delivery tube and in the region of the thick-stock conveyor. A high delivery capacity with a given speed is thus achieved.

A further metering of liquefaction water can take place in the region of the inlet, such as for example at a feeding chute for the delivered medium. The chute thus acts as a gravity buffer, whilst it is ensured by means of a control that the ratio of the dumping height, which is ascertained for example by a radar measurement, to a hydraulic height, which is ascertained for example by a pressure transducer, is kept in a preset range. If this range is adhered to, the values of the stock density and, with at a given speed on the spiral or the helix of the thick-stock conveyor, the driving power of the shaft remain in a narrow range.

The liquid intake can be constituted such that it imparts a swirling motion to the liquid, so that the delivered medium enters as an eddy flow into a downstream conveyor.

The invention is based on the knowledge that a standard conveyor with a delivery tube and a rotatable spiral can be used as a liquefier if water intakes are disposed at in the funnel. According to an aspect to the invention, therefore, the medium to be delivered is not first diluted to an optimum delivery consistency, but rather the delivery tube itself and in particular the funnel are constituted as a liquefier. This makes it possible to deliver the delivery medium during the addition of water and at the same time to mix it with the water.

The addition of water in the region of the delivery tube ensures that the thick-stock conveyor is lubricated by the added water in its radial outer region between the spiral and the delivery tube and that a high degree of dilution and therefore a low resistance thus arises precisely on this region. It is therefore proposed that auxiliary liquid intakes are disposed on the delivery tube, said auxiliary intakes also being able to be flange-mounted tangentially on the delivery tube.

Fortunately, it has emerged that the addition of water at the funnel and, as the case may be, also at the delivery tube has led to a marked reduction in the require delivery energy. Jamming of large particles between the delivery tube and the rotatable spiral is also prevented by the flushing effect brought about by the addition of water.

The thick-stock conveyor can be a spiral or a screw. A screw is particularly advantageous.

In order also to convey the medium actively onwards in the region of the funnel, it is proposed that there is disposed in the region of the funnel an end of the thick-stock conveyor whose external diameter tapers corresponding to the funnel.

With regard to the diameter of the cylindrical delivery tube and in particular the funnel, it is proposed that the passage width of the thick-stock conveyor in the delivery tube increases from the inlet to the outlet. This permits the delivery tube spiral to be adapted to the geometrical dimensions of the delivery tube and to the flow-related requirements caused by the increase in volume.

As an advantageous embodiment of a downstream conveyor, it is proposed that the centrifugal pump is disposed directly at the tapered end of the funnel.

A structurally simple design results if the thick-stock conveyor, the funnel and the pump are disposed on a straight line. A compact liquefier thus arises, which enables onward delivery at right angles to the line when use is made of a centrifugal pump.

It is advantageous if the liquefier comprises, at the inlet of the delivery tube, an intake disposed at right angles to the thick-stock conveyor. The material thus flows into the thick-stock conveyor from the side and the fitting of a drive, for example of a screw, is thus facilitated.

Precisely in the case of lumpy media difficult to convey, a blockage or high degree of friction between the thick-stock conveyor and the cylindrical delivery tube can arise at the inlet of the liquefier, at which sufficient liquefaction is still not present. It is therefore proposed that the delivery tube comprises a widened portion at the transition from the intake to the delivery tube. This ensures that the medium can easily be drawn into the delivery tube.

In order to influence the intake to the thick-stock conveyor in a flow-related manner, it is proposed that the intake comprises a constriction at the transition to the delivery tube. This constriction then preferably lies on the side of the widened portion and can for example be disposed above the widened portion. This constriction leads to an inclined surface, which forces the medium into the region of the start of the thick-stock conveyor, in order to avoid clogging-up at the transition between the intake and the cylindrical delivery tube.

For optimum control of the operating states of the liquefier, it is proposed that a dumping height measuring device is disposed in the intake. This can take place by means of a radar measurement, an ultrasound measurement or an optical detection.

Moreover, it is advantageous if a measuring device for determining the hydrostatic pressure is disposed in the intake or in the delivery tube. This can be a pressure load cell disposed in the lower region of the liquefier.

A simple separation of different delivered materials is achieved by the fact that the pump and a cyclone thereon are disposed at the outlet of the delivery tube. Depending on the solvent used, such as for example water, alcohol or salt water, the density of the solvent can then lead to a different separation effect.

A line from the liquid outlet of the hydrocyclone directly before the inlet of the centrifugal pump is advantageous from the energy standpoint. The circulation volume flow returning from the cyclone can thus be added directly before the inlet of the centrifugal pump. The flow line of the circulation volume flow returning from the cyclone then goes, more or less uninterrupted, directly before the inlet of the pump, as result of which the driving power can be reduced.

The problem underlying the invention is also solved by a method for operating such a liquefier, wherein the material to be treated is pre-treated in a solid-stock storage unit with a total stock density of more than 15% GG total consistency, the total stock density is then reduced in the liquefier to less than 10% GG and the liquefied material is delivered onward with a centrifugal pump.

The density in the solid-stock storage unit preferably lies at approx. 2 to 8% GG total stock density. Whereas, with standard solid-stock buffers such as conventional pulpers, the density lies at approx. 20% G, the volume of the solid-stock storage unit, a pulper or a conditioner is reduced to approx. ⅓ or ¼ by the liquefier. As a possible conditioner which can be used together with the liquefier, reference is made to the entire contents of PCT/DE2013/000129.

It is particularly advantageous if the liquefied material is delivered from the centrifugal pump into a cyclone, preferably into a hydrocyclone, and is fractionated there. A fractionator for virtually all the usual kinds of waste is thus made available.

Different materials can be separated depending on the liquid used in the hydrocyclone. If water mixed with salt is used in the hydrocyclone for materials that are heavier than water, such materials can be separated. Materials that are lighter than water can be separated for example with alcohol. A flow of separation can also be used.

A fraction can be delivered from the cyclone back into the solid-stock storage unit as part of a batch process and also a continuous process.

As part of a multiple circulation and also of a charge operation, a high overall degree of enrichment can be achieved even with a low enrichment efficiency in the overflow. Even if only 1% of a specific fraction is removed in the cyclone, the enrichment efficiency rises to a predetermined value after several runs.

The enrichment can be achieved by the cyclone and/or a conditioner. It is therefore advantageous if the solid-stock storage unit is a conditioner with an agitator and a sieve, in which a fraction, such as in particular fibrous material, is separated from the material by the sieve. The combination of a preparation unit with a hydrocyclone makes it possible, for example, to separate fibrous material from wastes from the paper industry in the conditioner by means of the sieve and to separate plastics in the hydrocyclone.

Depending on the material to be processed, a blockage may form at the immersion tube of the cyclone, said blockage being due to coarse material accumulating there. Even removal of the immersion tube does not lead to prevention of blockages, since the blockages then form in a downstream line segment. Size-reduction of the material before the separation of a specific material fraction would be expensive and ineffective. It is therefore proposed to draw off the liquid fraction from the cyclone through a preferably polished cone

It is advantageous if at least 50% of the liquid is added in the region of the outlet of the delivery tube.

It is advantageous if the pressure of the delivered material is measured in the liquefier. The pressure can be measured at different points in order to control the drive of the rotatable spiral. Roughly a constant filling height of the medium should be present at the inlet of the liquefier, said filling height essentially being determined by the power of the drive of the downstream pump and in particular of the centrifugal pump.

An advantageous method makes provision such that pressurised water is added at the delivery tube and the value measured in the liquefier is used to control a water intake to the delivered material.

Moreover, it may be advantageous if the value measured in the liquefier is used to control a drive of the rotatable spiral.

In addition or alternatively, provision is made such that the value measured in the liquefier is used to control a drive of a pump downstream of the delivery section.

An optimum control can be achieved by the fact that, during the operation of the liquefier, the distance between the dumping height and the height of the liquid in the liquefier is kept in a predetermined range.

It is thus possible to replace longer delivery sections, over which the delivery was hitherto carried out with screw or belt conveyors, by pipes in which the material to be delivered is pumped.

In the area of the paper industry and the recovery of fibrous materials from residual materials for example, an intermediate liquefaction of the material to be delivered leads to an increase in the reliability of the conveyor equipment, particularly since screw conveyors and helixes are subject to failure and wear.

Especially when use is made of a compactor and a liquefier, the water occurring in the compactor can be added to a liquefier simultaneously or with a time lag. An effective delivery section is thus enabled, over which particularly viscous material can be pumped by means of an intermediate liquefaction so as to overcome heights, to deliver in the bend and to move larger volumes inside the delivery section effectively and with little susceptibility to malfunction.

An example of embodiment of a liquefier is shown in the figure and is explained in greater detail below.

In the figures:

FIG. 1 shows a cross-section through a liquefier,

FIG. 2 shows a first plant with a conditioner, a liquefier and a hydrocyclone and

FIG. 3 shows a second plant with a conditioner, a liquefier and a hydrocyclone.

Liquefier 1 has a cylindrical delivery tube 2, in which a rotatable spiral 3 is disposed as a thick-stock conveyor. Cylindrical delivery tube 2 comprises an inlet 4 and an outlet 5. Provided along delivery tube 2 are water intakes 6, 7, via which pressurised water is pressed into the cylindrical delivery tube. Disposed at outlet 5 of cylindrical delivery tube 2 is a funnel 8, which also comprises a water intake 9. A spiral 3 of a screw is constituted as a cross-sectionally tapering spiral 10 in this funnel 8. The spiral 3 has a slightly increasing pitch from inlet 4 to outlet 5 and a constant spiral diameter in the region of the cylindrical delivery tube.

A pump 12 is disposed at tapered end 11 of funnel 8. This pump is a centrifugal pump, which is flange-mounted centrally on tapered end 11 of funnel 8 and delivers the liquefied medium radially via outlet 13 into a pipe (not shown).

Provided at inlet 4 of delivery tube 2 is an intake 14, which leads the medium radially to spiral 3. Intake 14 has an opening 15, which is connected for example to the outlet of a pulper, from which the medium is conveyed to liquefier 1.

The distance between spiral 3 and delivery tube 2 is enlarged at inlet 4 of the cylindrical delivery tube, in that a widened portion 16 is provided at the transition from intake 14 to delivery tube 2. Furthermore, intake 14 comprises a constriction 17 at the transition to delivery tube 2.

Provided at the bottom of delivery tube 2 is a measuring device 18 for determining the hydrostatic pressure, which delivers a measurement value corresponding to the height of the water level in delivery tube 2 or in intake 14, said measurement value being used to control drive 19 of spiral 3 and drive 20 of pump 12. The height of the supplied medium is ascertained with the radar measurement serving as a dumping height measuring device 21.

FIG. 2 shows the interaction of liquefier 1 shown in FIG. 1 with an upstream conditioner 30 and a downstream hydrocyclone 31.

The raw material to be treated is fed with water to conditioner 30 in the region of arrow 32 and is circulated there with screw 33 in order to separate coarse materials 35 above sieve 34. After a material collector 36, an outlet 37 is provided for free fibrous material and dissolved substances which pass through the sieve.

Heavy parts remaining on the sieve are removed from conditioner 30 via a heavy parts trap 38. Beneath screw 33, the materials are moved by a displacement spiral 39 via sieve 34. The function of the conditioner and alternative conditioners that can be used for this purpose are described in WO 2013/135224, to the entire contents of which reference is made.

The materials which are not heavy parts and which are not separated out by the sieve pass into liquefier 1 and are diluted there with water. The diluted material is then added to hydrocyclone 31 via centrifugal pump 12 and thick pipe lines with slightly curved bends. The thickness of the pipe lines and the slightly curved bends are intended to ensure a low resistance in the line between centrifugal pump 12 and hydrocyclone 31. Sinking materials are separated from floating materials in hydrocyclone 31. The sinking materials are removed following arrow 40 and the floating materials are removed from the hydrocyclone with the water following arrow 41 and essentially fed again to liquefier 1. Before this, a partial flow 42 can be separated in order to remove solids and a partial flow 43 can be fed back to conditioner 30. A liquid with a density differing from that of water, for example an alcohol or an oil, can be used in the liquefier and in the hydrocyclone for the separation.

A further embodiment of a plant according to the invention is shown in FIG. 3. Material extractor 50 shown there separates, using a sieve 51, supplied material 52 into material 53 passing through the sieve and a material flow 54, which is removed from the material extractor 50 above sieve 51. The material extractor is operated with a material density of at approx. 20% GG and material 54 is then fed in a gravity buffer 55 of liquefier 56.

The material from material extractor 50 and new material 49 is collected in gravity buffer 55, material dumping height 58 is measured with a radar 57 and liquid a height 60 is ascertained with pressure transducer 59. Material dumping height and liquid height serve to control screw 61 and centrifugal pump 62.

A heavy parts trap 48 beneath screw 61 is disposed at the underside of gravity buffer 55. This heavy parts trap can be constituted as a drawer. A simple lowered section in the bottom region is however also sufficient, in which extremely heavy parts such as steel balls, very large stones, crusher teeth etc. collect. They can be removed from there in order that they do not damage the plant.

The transition geometry at the intake of conical delivery tube 63 in region 64 is relevant. As described above, transfer angle 65 must not be selected too great to avoid strong compression. In order that inhomogeneities, such as in particular pieces of wood, do not get jammed between the screw and the edge, the angle should also not be too small. The spiral of screw 61 is adapted with the increasing pitch to the increasingly narrow cross-section.

The tube of liquefier 56 is slightly conical and has a diameter between 0.6 and 1.0 m, whilst the inlet cross-section of the centrifugal pump lies between 0.3 and 0.5. The inflow from the hydrocyclone 66 enters in region 67 at the transition between liquefier 56 and centrifugal pump 62. This inflow prevents clogging-up of the conical tube of liquefier 56 at the transition to centrifugal pump 62.

The feeding of the liquefied material flow from centrifugal pump 62 to hydrocyclone 66 takes place in wide bends 68. Hydrocyclone 66 has an inner polished, conical head 69, which enables the floating of films and olefins without the risk of clogging-up. Such coarse materials pass from conical head 69 into a line 47 with a diameter of 400 mm and can be removed from the system for example at outlet 70. Conical head 69 prevents, especially when it is polished, clogging-up of the access to line 47 by floating material, which can otherwise get caught there and then block the outlet to line 47.

The return of the overflow of hydrocyclone 66 to centrifugal pump 62 also takes place via wide bends with a large internal diameter, for example 0.4 m, before the pump inlet in such a way that the change in impulse required for this is minimal at the moment of interruption of the flow line at the point of the material inflow. This leads to a smaller energy loss. The centrifugal pump thus becomes the turbine and the tendency to clogging-up is markedly reduced.

Provided at outlet 70 is a branch approx. at 90° with respect to straight flow direction 71, so that the main impulse of the material flow takes place according to arrow 71 in the direction of the centrifugal pump and a certain pressure rise as in a suction line is brought about by the 90°-angled outlet 70 as a result of the impulse deflection. Outlet 71 is preferably constituted without a closure element, in such a way that a partial flow can be removed there and can be fed to material extractor 50. A circuit thus arises, in that outlet 70 is connected to inlet 46. In this case, it is advantageous if material flow 54 is split up before being fed to gravity buffer 55, in such a way that the olefins, films etc. are separated out and do not get into gravity buffer 55.

Cyclone 66 is constructed slender and high in order to bring about a long eddy flow 72. Lower deflection point 73 should lie before settling chamber 74 and not in the settling chamber. Provided between conical region 75 of hydrocyclone 66 and its settling chamber 74 is a water ring chamber 76, which comprises a perforated plate 77, in order to feed through the perforated plate, in a finely dosed manner, precisely the quantity of water that is required for the fractionating flow separation. The water feed is indicated by arrow 78.

Settling chamber 74 is operated continuously and an adjoining heavy parts trap 79 is operated periodically. Slide gate valves 80 and 81 are provided for this purpose. The material removed as an underflow in the hydrocyclone is carried away by a carrying conveyor 82.

The plants shown are particularly well suited for the recycling of fibrous materials, such as for example from beverage carton plastics. 

1. A liquefier (1) with a delivery tube (2), which comprises an inlet (4) and an outlet (5) and in which a thick-stock conveyor (3) is disposed, wherein a centrifugal pump (12) is disposed at the outlet (5) of the delivery tube (2).
 2. The liquefier according to claim 1, wherein a main liquid intake (9) is disposed at the outlet of the delivery tube and before the centrifugal pump.
 3. The liquefier according to claim 1, wherein the main liquid intake has a directional component in the direction of the axis of the delivery tube (2).
 4. The liquefier according to claim 1, wherein the main liquid intake has a directional component in the direction of a circumferential line of the delivery tube (2).
 5. The liquefier according to claim 1, wherein a funnel (8) is disposed at the outlet (5) of the delivery tube (2).
 6. The liquefier according to claim 5, wherein an end of the thick-stock conveyor (3), the external diameter whereof tapers corresponding to the funnel (8), is disposed in the region of the funnel (8).
 7. The liquefier according to claim 5, wherein the centrifugal pump (12) is disposed directly at the tapered end (11) of the funnel (8).
 8. The liquefier according to claim 5, wherein the thick-stock conveyor (3), the funnel (8) and the centrifugal pump (12) are disposed on a straight line.
 9. The liquefier according to claim 1, wherein the thick-stock conveyor (3) is a screw.
 10. The liquefier according to claim 1, wherein the passage width of the thick-stock conveyor (3) in the delivery tube (2) increases from the inlet (4) to the outlet (5).
 11. The liquefier according to claim 1, wherein at the inlet (4) of the delivery tube (2), an intake (14) is disposed at right angles to the delivery direction of the thick-stock conveyor (3).
 12. The liquefier according to claim 11, wherein the delivery tube (2) comprises a widened portion (16) at the transition from the intake (14) to the delivery tube (2).
 13. The liquefier according to claim 11, wherein the intake (14) comprises a constriction (17) at the transition to the delivery tube (2).
 14. The liquefier according to claim 11, wherein a dumping height measuring device (21) is disposed in the intake (14).
 15. The liquefier according to claim 11, wherein a measuring device (18) for determining the hydrostatic pressure is disposed in the intake (14) or in the delivery tube (2).
 16. The liquefier according to claim 1, wherein auxiliary liquid intakes (6, 7) are disposed on the delivery tube (2).
 17. The liquefier according to claim 1, wherein a hydrocyclone is disposed at the outlet (5) of the centrifugal pump (12) and following the latter in the flow direction.
 18. The liquefier according to claim 17, wherein a line leads from the liquid outlet of the hydrocyclone directly before the inlet of the centrifugal pump (12).
 19. A method for operating a liquefier according to claim 1, wherein the material to be treated is pre-treated in a solid-stock storage unit with a total stock density of more than 15% GG total stock density, the total stock density is then reduced in the liquefier (56) to less than 10% GG, preferably less than 5% GG, and the liquefied material is delivered onward with a centrifugal pump (12).
 20. The method according to claim 19, wherein the liquefied material is delivered from the centrifugal pump (12) into a cyclone (66), preferably into a hydrocyclone, and is fractionated there.
 21. The method according to claim 20, wherein a fraction is delivered from the cyclone (66) back into the solid-stock storage unit.
 22. The method according to claim 1, wherein the solid-stock storage unit is a conditioner (30) with an agitator and a sieve (51), in which a fraction, such as in particular fibrous material, is separated from the material by the sieve (51).
 23. The method according to claim 22, wherein the liquid fraction is drawn off from the cyclone (66) through a preferably polished cone.
 24. The method according to claim 1, wherein at least 50% of the liquid is added in the region of the outlet of the delivery tube (2).
 25. The method according to claim 1, wherein the pressure of the delivered material is measured in the liquefier (56).
 26. The method according to claim 25, wherein during the operation of the liquefier (56), the distance between the dumping height and the height of the liquid in the liquefier (56) is measured and kept in a predetermined range.
 27. The method according to claim 25, wherein pressurised water is added at the delivery tube (2) and/or at the outlet (5) of the delivery tube (2) and the value measured in the liquefier (56) is used to control a water intake (12) to the delivered material.
 28. The method according to claim 25, wherein the value measured in the liquefier (56) is used to control a drive (19) of the thick-stock conveyor (3).
 29. The method according to claim 25, wherein the value measured in the liquefier (56) is used to control a drive (20) of a pump (35) downstream of the delivery section. 